In research and development, medical diagnosis and examination, and agricultural testing in fields such as biology and pharmaceutical sciences, liquid from picoliters (pL) to microliters (μL) is dispensed to each of different subjects. For example, an operation to dispense small volumes of liquid is carried out to determine effective concentration of a chemical compound that attacks cancer cells.
Such an operation is generally referred to as a dosage response experiment, and during the operation, a chemical compound of a large number of different concentrations is prepared in containers such as wells of a microplate in order to determine effective concentrations of the chemical compound. An on-demand type liquid droplet ejecting apparatus is used for that operation. For example, the liquid droplet ejecting apparatus includes a solution container, a nozzle that discharges the solution, a pressure chamber that is disposed between the solution container and the nozzle, and an actuator that controls pressure of the solution in the pressure chamber.
According to such a liquid droplet ejecting apparatus, the amount of liquid of a single droplet that is discharged from the nozzle is of the order of picoliters, and it is possible to drip a liquid of the order of picoliters to microliters into each well by controlling the number of times of dripping. Therefore, the liquid droplet ejecting apparatus is suitable for dispensing compounds of a large number of different concentrations, by minute amounts from pL to nanoliters (nL) and microliters (μL).
Organic matter is commonly adhered to inner surfaces of a liquid flow channel of the liquid droplet ejecting apparatus that contact the solution. In order to discharge a solution containing less impurities from the liquid droplet ejecting apparatus, it is necessary to perform cleaning to remove the organic matter on the inner surfaces of the liquid flow channel of the liquid droplet ejecting apparatus. To clean the inner surfaces of the liquid flow channel, a cleaning solution is typically used.
To clean the inner surface with the cleaning solution, there are three steps: a step of filling a cleaning solution; a step of removing the cleaning solution from the inner surfaces; and a step of drying the inner surfaces. This cleaning method with the cleaning solution may take a significant amount of time. Thus, there is a need for liquid ejection apparatus that can be quickly and effectively cleaned.